The amount of excess travel in the United States is estimated on the basis of past research and new empirical studies Excess travel is defined as the arithmetic difference between total actual highway use, exclusive of destination-free "pleasure" driving, and the use that would have resulted if all such travel had been made by using the optimum route connecting each individual origin-destination pair Excess travel is shown to be caused by a number of different factors acting singly or in combination These include route selection criteria and efficiencies in necessary route-planning information, in the highway information system, and in both route-planning and route-following skills The synthesis of all available data indicates that excess travel contributes 4 percent of all vehicle miles of travel and 7 percent of all travel time for work-related trips Corresponding figures for non-work-related trips are 20 and 40 percent, respectively Applying these proportions to total US travel results in a total of excess travel amounting to 835 billion mi and 914,000 person-years per year at a total estimated cost of more than $45 billion

Excess travel: causes, extent, and consequences

A number of important considerations are identified, and information on how they are being addressed by the Administration is presented Seven basic human factors-related questions are used as a conceptual framework for identifying these considerations, and for describing how they might be addressed These are: (1) Why do drivers need navigation information? (2) What information do they need? (3) When do they need it? (4) Where should it be located? (5) How should it be displayed and accessed? (6) Who are the users and what are their characteristics? (7) Can they use the systems effectively? It is concluded that it is important that government, private industry, electronics engineers, and human factors specialists work together to produce optimum systems configurations for the motoring public >

Human factor considerations of motorist navigation and information systems

Highway-freeway interchanges can be a source of confusion to unfamiliar drivers. Typically, freeway entrance ramp information is provided by means of trailblazer assemblies (interstate or highway shield, cardinal direction, and a small white arrow on a blue shield). Trailblazer assemblies are generally located right at the interchange location, giving unfamiliar drivers very little advance notification as to the proper lane choice needed to gain access to the freeway entrance. Advance located ground mounted diagrammatic guide signs provide this much needed information well in advance of the interchange entrance, thus giving drivers more time to change lanes, if needed. Diagrammatic signs have been used in Europe for many years with great success. The present study investigated the effectiveness of ground mounted diagrammatic signs in the context of urban multi-lane arterials leading to a freeway. The diagrammatic sign layout was designed as part of this project in collaboration with the Ohio Department of Transportation (ODOT). Six highway-freeway interchanges were selected in the Greater Columbus, Ohio, area to determine the effectiveness of the diagrammatic signs in the field. Traffic flow video footage was collected at the selected sites before the diagrammatic signs were installed. The finalized diagrammatic sign designs were then installed and the traffic flow videotaping was repeated. The collected video footage was automatically analyzed with Mobilizer PC. The resulting vehicle count, speed, and headway data were used as input to a closed form analytical model to determine the probability that drivers could successfully change lanes as needed, prior to reaching the gore of the freeway entrance. The theoretical analysis indicated a much higher probability that an unfamiliar driver could execute a required lane change when diagrammatic signs are used. ODOT/Federal Highway Administration evaluators visited the six interchange sites and provided their input and opinions as to the use of diagrammatic signs. The vast majority of the evaluators fully embraced the idea of diagrammatic signs. Eye movement recordings were performed at night at the six sites in order to determine if the presence of the diagrammatic signs was distracting. The results of the eye movement analysis indicate that the diagrammatic signs are not looked at excessively often or excessively long. The overall median first look distance to the diagrammatic signs was found to be 125 m. An evaluation with unfamiliar test drivers corroborated the findings of the theoretical model analysis, in that drivers were able to execute a needed lane change much earlier when diagrammatic signs were provided. A set of application guidelines for diagrammatic signs is provided.

Evaluation of ground mounted diagrammatic entrance ramp approach signs

A comprehensive questionnaire dealing with all aspects of urban guidance was prepared, field-tested, and distributed nationwide, and 727 usable returns were received. Portions of the questionnaire dealing with trip plan preparation and trip plan execution are analyzed in this paper. Analyses of the returned questionnaire were made separately in terms of "stranger" and "local stranger" trips. Although there was a significant difference in the proportion of each class of respondent insofar as the preparation of a written trip plan is concerned, differences in the relative importance of perceived information needs and problems were less than expected. Almost half of all respondents reported feeling lost at some state of their most recent trip. Of these, about half were actually lost. Rank ordering of problem types showed that most of those ranking high dealt with difficulties in arterial navigation. Maps were found to be the most important element used in trip plan preparation; map availability and map usability were correspondingly found to rank very high as problem types for stranger trips. Route numbers and street names and numbers were found to rank first or second among needed information types for all classes of respondents.

Urban guidance: perceived needs and problems

Previously developed highway information system research techniques were used to assess the State of the Art of Urban guidance and to study means of Urban guidance and to study means of overcoming existing deficiencies. Recently published literature was surveyed and technical discussions wer conducted with experts and operational personnel. The response to a nationwide questionnaire survey was analyzed in an attempt to determine and characterize guidance information needs and driver-pereceived guidance problems in urban areas. Guidance missions were conducted in representive urban areas and case studies were prepared. The results of the foregoing studies were then synthesized, and problems and potential solutions were identified. A representative urban area was then selected and the problem-solution pair was applied. The problem-solution pairs were evaluated in laboratory simulation. The results of the research were then used to prepare a list of recommendations. The published literature in system elements, systems considerations and user-perceived problems and needs is reviewed. Study inputs yielded in the synthesis of the State of the Art (including both the literature survey and technical discussions) are listed. A summary is presented of a study of the 1971 edition of the Manual on Uniform Traffic Control Devices. Details are given of the purpose and methodology of the case studies in urban guidance. The questionnaire survey is described and signing solutions are discussed. The empirical evaluation of some signing solutions are reviewed. The results of the study are interpreted and discussed in the light of system deficiencies and alternate or revised solutions. Conclusions regarding the scope of the urban guidance problem and recommendations relating to the problem are presented. The applications of the research are discussed and areas of research are suggested.

G F King

Papers

Urban area highway guide signing